Duration is just the two times, in the same units
To find how long something lasted, convert both times to a single scale — minutes past midnight is easiest — and subtract. The calculator does this in seconds so it never loses the odd minute or second.
The only real trap is 12-hour clock time. 12 AM is midnight (00:00) and 12 PM is noon (12:00) — they are not interchangeable. Convert to a 24-hour clock first and the subtraction is trivial.
Minutes, decimal hours and days — same span, three units
| Clock reading | Total minutes | Decimal hours | As days |
|---|---|---|---|
| 1 hr 30 min | 90 | 1.50 | 0.0625 |
| 5 hr 30 min | 330 | 5.50 | 0.229 |
| 8 hr 0 min | 480 | 8.00 | 0.333 |
| 9 hr 30 min | 570 | 9.50 | 0.396 |
| 24 hr 0 min | 1,440 | 24.00 | 1.000 |
To convert minutes to decimal hours, divide by 60: 45 minutes is 45 ÷ 60 = 0.75. A full day is 1,440 minutes or 86,400 seconds.
The overnight case: why the end time looks smaller
When a shift crosses midnight, the end reading on the clock is lower than the start, so a plain subtraction goes negative. Adding 24 hours to the end fixes it — the same 8-hour span, just measured across the day boundary.
If the end time is earlier on the clock than the start, the true end is on the next day — add 24 hours before subtracting.
- Breaks — a paid-hours figure subtracts unpaid lunch: an 8-hour span with a 1-hour break is 7 worked hours.
- Time zones — this measures elapsed time within one zone; convert both readings to the same zone first if they differ.
Common questions
How do I work out hours between two times in my head?
Count up to the next whole hour, then count whole hours, then the leftover minutes. From a quarter past to a half past five hours later is 45 minutes plus 4 hours plus 30 minutes, so 5 hours 15 minutes.
How does the calculator handle an overnight shift?
If the end time is earlier than the start time, it assumes the end is on the next day and adds 24 hours. So a late-evening start ending in the early morning comes out positive, not negative.
What are decimal hours and why does payroll use them?
Decimal hours express minutes as a fraction of an hour: 30 minutes is 0.5, 15 minutes is 0.25, 6 minutes is 0.1. Payroll multiplies decimal hours by the pay rate, which is cleaner than working in hours and minutes.
